Rapid progress in genomics, proteomics, and cell analysis has pushed the biotechnology sector to develop faster and more efficient devices for analyzing biological samples. Accordingly, the biotechnology sector has directed substantial effort toward developing miniaturized microfluidic devices, often termed labs-on-a-chip, for sample manipulation and analysis. Such devices may analyze samples in small volumes of liquid, providing more economical use of reagents and samples, and in some cases dramatically speeding up assays. These devices offer the future possibility of human health assessment, genetic screening, and pathogen detection as routine, relatively low-cost procedures carried out very rapidly in a clinical setting or in the field. In addition, these devices have many other applications for manipulation and/or analysis of nonbiological samples.
Some microfluidic devices are configured to process samples in microfluidic chambers using electrical circuitry. Such microfluidic devices may be configured so that electrical devices provided by the electrical circuitry process samples in the chambers. In some cases, the electrical devices may include heaters to heat fluid in the chambers, for example, to accelerate the rate of a chemical or enzymatic reaction. In other cases, the electrical devices may include electrodes used to form an electric field to move charged molecules and/or fluid within the chambers. However, with very small fluid chambers, space for electrical devices may become limited and independent control of the electrical devices may not be possible. Accordingly, processing capabilities within the fluid chambers may be compromised by a need to select one type of device over another to occupy the limited space available.
The problems associated with limited space may be particularly apparent with temperature control. For example, it may be desirable to perform two or more reactions at distinct temperatures within a chamber or set of closely spaced chambers in a microfluidic device. In addition to problems associated with positioning a sufficient number of thermal control devices in the available space, the temperature of one reaction may interfere with the ability to maintain a desired temperature for the other closely spaced reaction(s) due to insufficient thermal insulation between the reactions. This insulation problem may become more acute when the temperatures of the reactions are very different. Spatially separating the reactions by a greater distance may improve thermal insulation between the reactions, but at the expense of a decreased density of chambers and thus reduced capability of the microfluidic device.